Levette also claimed Siri had previously closed the store early, taken sick leave without justification and been late for his shifts.
But yesterday, the Fair Work Commission found Siri had been unfairly dismissed.
"This unnecessarily harsh approach was compounded by the extraordinarily heartless disregard for the personal circumstances of another human being who was suffering from pancreatic cancer," commissioner Ian Cambridge said.
" … the reason for the dismissal of the applicant was not sound, defensible or well-founded. There was not a valid reason for the dismissal of the applicant related to his capacity or conduct."
Commissioner Cambridge said dismissing Siri over the phone was "plainly unjust, manifestly unreasonable, unnecessarily harsh, and in this case, unconscionably insensitive".
He originally ordered Urban Orchard to pay Siri A$26,000 in compensation.
However, that figure was then reduced by 20 per cent due to the "impact on the viability" of the company.
It was slashed by a further 10 per cent to account for Siri's likely further absence, meaning the former chef now looks set to receive A$18,200 in total.
However, Levette told the Sydney Morning Herald she was not aware of Siri's cancer, and the business would appeal the decision.
Shine Lawyers superannuation and employment law expert Will Barsby told news.com.au employees couldn't be "unfairly treated" for taking "reasonable and legitimate sick leave".
"Each case is considered on its merit by Fair Work," he said.
"You should check your workplace policy on sick leave and supply a doctor's certificate when needed — some workplaces require a certificate even for one day off.
"Be upfront with your boss about what is going on to see if there is any flexibility while you get treatment or recover."
Barsby said insurance could help take some of the strain off workers who fall seriously ill.
"If you do run out of sick leave when you are seriously ill or are forced to quit your job, then we always encourage people to check their superannuation policies for access to income protection insurance," he said.
"Depending on what your fund offers, it will pay you a percentage of your wage while you can't work.
"There is also access to total permanent disability insurance through superannuation that gives you a lump-sum payment if you become too sick to work or you are diagnosed as having a terminal disease. There is quite a lot of paperwork when you apply for these insurances, but seek legal advice if you need it."